Another very good way I found to keep track of (lots of) material is to use scientific archiving tools, such as Papers: it can collect tons of documents, add tags, authors, editors, publication dates, collections, etc., and sync everything with smartphones.

I’ve got thousands of news items, articles, books, extracts, long-reads where to look up for new ideas or references when I am writing. The only problem is that I do not remember things by heart anymore: I’m searching them in this personnal library.